## To Throw, or Not to Throw

With a runner on first, a pitcher’s approach to a batter changes in many ways. The most obvious is the delivery out of the stretch. More subtly, the pitcher can be distracted by the runner potentially stealing a base. To mitigate the runner’s chances of stealing a base, the pitcher has the option to throw over to first, thereby keeping the runner closer to the bag.

After a few throw overs, I often hear announcers remarking that the pitcher is “distracted” by the base runner, implying that the pitcher is compromising his effort to get the batter out. By expending his mental, and maybe also his physical, energy on the base runner, he commits less towards the batter. In this article, we attempt to demonstrate this proposed effect with a statistical analysis.

To study the effect of throw overs on a pitcher’s success with a batter, we look at the pitcher’s change in Win Expectancy (ΔWE) for all the batting events over four seasons, from 2007 to 2010. During this period, the average ΔWE for each batter is -2.3 bps*. Equivalently, batters had an average ΔWE of +2.3 bps for each plate appearance (PA). In other words, for the period observed, offense/hitters were stronger than defense/pitchers.

*Definition of bps: 1 bps is 1/100th of a percentage point. 100 bps = 1%.

In this period, there was a total 773,123 plate appearances (PAs). To observe trends related to the effects of pitcher throw overs (TOs), we look at the specific configuration where there is a runner on first and no other base. The data shows that there is not much difference in ΔWE when a pitcher TOs or does not TO.

Average ΔWE
TO & No TO: -6.745
No TO: -6.892
TO: -6.380

In fact, the results are counterintuitive: this view of the data indicates that throwing over results in a better ΔWE. In order to see what’s really happening, we dig deeper. The first breakout of data we perform is effect on lefty and righty pitchers. A lefty has the distinct advantage of being able to see the first-base runner, whereas a righty has his back to the runner. Mechanically, one expects a righty to be more out of his comfort zone than a lefty. In the time period observed, both lefties and righties TO 29% of the time.

Average ΔWE, by Pitcher Handedness
Lefty, Total +2.95
Lefty, No TO -0.18
Lefty TO +10.70
Righty, Total -10.61
Righty, No TO -9.56
Righty, TO -13.21

The lefty’s total average ΔWE is +2.95, whereas a righty has -10.61, a very stark difference. This is an indication of how much stronger a lefty is in this situation. In all base configurations (not just runner on first), the difference is much smaller: a lefty’s ΔWE is -1.70 and a righty’s ΔWE is -2.51. Hence, we see there is something unique about the runner-on-first situation. I find it more interesting comparing the pitchers’ differential with respect to TO or not. When a lefty throws over to first, his ΔWE increases dramatically (-0.18 vs 10.70), whereas righties have the opposite effect (-9.56 vs -13.21).

Intuitively, baseball fans assume that lefties are less distracted by the runner on first than righties. This difference in WE can serve as a pillar of statistical evidence.

A last point: Is ΔWE an appropriate metric to measure the pitcher’s level of distraction? I believe so, because ΔWE weights higher-pressure configurations (configuration = run differential, inning, base-out). This is precisely the situations that I believe the pitcher is more inclined to fall victim to being distracted by a runner on first. In non-pressure configurations, the pitcher typically ignores the runner. By using other metrics, we are implicitly saying a pitcher’s success when he is up by 10 runs and doesn’t TO is equivalent to his success when the game is tied and doesn’t TO.

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PhD in Applied Physics @Columbia University 3+ years in the Financial Services Industry Met fan

### 6 Responses to “To Throw, or Not to Throw”

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1. Kevin says:

Very cool analysis. Did you get to look at which individual pitchers earned the largest lift in ΔWE through throwing over? I’m curious if any righthanders bucked the trend?

Nice work, but you left out one thing that I was expecting to see based on the beginning of the article…

I was expecting to see something showing whether the number of throw overs has an effect on the pitcher’s performance. Sometimes they throw over once just to keep the runner honest. That’s a big difference from the way they used to throw over 10 times when Rickey Henderson was on first and second was open back in the 80s. I’d bet there would be some negative relationship between the number of throw overs and the impact on pitcher performance.

I’ll add this too… The most feared baserunners have typically been used as leadoff men. It’s entirely possible that the notion that they distract the pitcher is a result of really good hitters hitting behind them in the lineup. In fact, it’s conceivable that there are occasions when a pitcher throws over simply to buy time or clear their head as they make sure they know what they want to do with the batter.

4. Meninder Purewal says:

Kevin: Thanks for the comment. Application is always an important part of any analysis as a sanity check. I filtered for >400PAs (remember, this is PAs for man on first and no other base). Below is the top ten pitchers. The columns are Name, Handedness, Difference between avg delta WE with no TO and with TO (in bps), and % of PA where pitcher throws over.
Pitchers that fared worse:
Matt Garza, R,-452, 3%
Brett Myers, R,-140, 25%
Miguel Batista, R,-120, 30%
Josh Johnson, R,-116, 58%
Daniel Cabrera, R,-112, 19%
Nate Robertson, L,-91, 30%
Tim Lincecum, R,-90, 37%
Oliver Perez, L,-88, 16%
Tim Wakefield, R,-81, 33%

Pitchers that fared better:
John Lannan, L, 157, 25%
Jered Weaver, R,104, 35%
Scott Kazmir, L,88, 18%
Cliff Lee, L,74, 8%
Scott Baker, R,74, 23%
John Danks, L,70, 40%
Bronson Arroyo, R,68, 28%
Fausto Carmona, R,59, 26%